Question: Omar starts counting at 42, and he counts by threes. If 42 is the 1st number that Omar counts. what is the 14th number that he counts?
Solution: What is the first number that he counts? $42$ What is the second number that he counts? $\begin{align*}&42 + 3 \\ &= 45\end{align*}$ What is the third number that he counts? $\begin{align*}&42 + 3 + 3 \\ &= 42 + (2 \times 3) \\ &= 48\end{align*}$ What is the 14th number that he counts? $\begin{align*}&42 + (13\times3) \\ &= 42 + 39 \\ &= 81\end{align*}$